You are what you eat, or so the saying goes. But Richard Wrangham, of Harvard University, believes that this is true in a more profound sense than the one implied by the old proverb. It is not just you who are what you eat, but the entire human species. And with Homo sapiens, what makes the species unique in Dr. Wrangham's opinion is that its food is so often cooked. Cooking is a human universal. No society is without it. No one other than a few faddists tries to survive on raw food alone. And the consumption of a cooked meal in the evening, usually in the company of family and friends, is normal in every known society. Moreover, without cooking, the human brain(which consumes 20-25% of the body's energy)could not keep running. Dr. Wrangham thus believes that cooking and humanity have developed alongside. In fact, as he outlined to the American Association for the Advancement of Science(AAAS), in Chicago, he thinks that cooking and other forms of preparing food are humanity's "killer application": the evolutionary change that underpins all of the other—and subsequent—changes that have made people such unusual animals. Humans became human, as it were, with the emergence 1.8 million years ago of a species called Homo erectus. This had a skeleton much like modern man's—a big, brain-filled skull and a narrow pelvis and rib cage, which imply a small abdomen and thus a small gut. Hitherto, the explanation for this shift from the smaller skulls and wider pelvises of man's apelike ancestors has been a shift from a vegetable-based diet to a meat-based one. Meat has more calories than plant matter, the theory went. A smaller gut could therefore support a larger brain. Dr. Wrangham disagrees. When you do the sums, he argues, raw meat is still insufficient to bridge the gap. He points out that even modern "raw foodists", members of a town-dwelling, back-to-nature social movement, struggle to maintain their weight—and they have access to animals and plants that have been bred for the table. Pre-agricultural man confined to raw food would have starved. Start cooking, however, and things change radically. Cooking alters food in three important ways. It breaks starch molecules into more digestible fragments. It "denatures" protein molecules, so that their amino-acid chains unfold and digestive enzymes can attack them more easily. And heat physically softens food. That makes it easier to digest, so even though the stuff is no more calorific, the body uses fewer calories dealing with it.
单选题
It can be inferred from the first paragraph that